Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$45.44	8.351%	$49.2347	$49.23	$49.25	$49.20
Purchase #2	$147.55	11.195%	$164.0682	$164.07	$164.05	$164.10
Purchase #3	$101.89	9.152%	$111.215	$111.22	$111.20	$111.20
Purchase #4	$21.41	5.411%	$22.5685	$22.57	$22.55	$22.60
Purchase #5	$25.74	10.390%	$28.4144	$28.41	$28.40	$28.40
Purchase #6	$5.47	11.774%	$6.114	$6.11	$6.10	$6.10
Purchase #7	$37.79	5.678%	$39.9357	$39.94	$39.95	$39.90
7 purchase totals =	$385.29		$421.5505	$421.55	$421.50	$421.50